The book is similar to the Book of Cain, depicting in-universe writing and illustrations. Such writings/artwork comes from characters such as Tyrael, Leah, and Deckard Cain. The book also features a fully removable family tree,[1] depicting the normal and corrupted versions of Leoric's family line.[2]

One of the most exciting and visceral action role-playing games in recent memory, Diablo® has become a worldwide gaming phenomenon. Diablo III: Book of Tyrael takes fans even further into the universe with a detailed and beautifully crafted artifact that focuses on the renowned champion Tyrael. As a former archangel of the High Heavens, he ranks among the most important and influential characters in the Diablo franchise. Here, in this illustrated and comprehensive tome, he reveals never-before-known secrets about the history of the world, the dark threats that yet face mankind, and his decision to join the ranks of humanity as a mortal. In Tyrael’s own words, “Forevermore we shall stand together, angels and men, in the light of this glorious new dawn.”[3]

Book of Tyrael followed up from Book of Cain in as much that it was to cover material that the original sourcebook did not have time or room to cover (e.g. Adria's backstory). Additionally, it was designed to tie-in with game content and serve as a bridge between Diablo III and Reaper of Souls. The book was originally going to be titled "Book of Leah," featuring Leah's notes, and the book's structure and tome reflecting this. Originally, Tyrael would take over in terms of the in-universe writing. As the book was developed, the writers realized that the book was really Tyrael's, so the name was changed along with other adjustments. Leah herself was the focus of additional character development.

Other examples of cut content include the faction and character lists. However, even these were subject to time and space constraints. Cut info may be implemented in a future tome.[4]